helmsman vs Jack-tar

helmsman and Jack-tar both are nouns.

Word	Noun	Adjective	Verb	Adverb
helmsman	Yes	No	No	No
Jack-tar	Yes	No	No	No

As nouns, Jack-tar is a hypernym of helmsman; that is, Jack-tar is a word with a broader meaning than helmsman:

Other hypernyms of helmsman include gob, Jack, mariner, old salt, sea dog, seafarer, seaman, tar.

helmsman (noun)	Jack-tar (noun)
the person who steers a ship	a man who serves as a sailor